The Hardening Soil model is an advanced model for the simulation of soil behaviour. As for the Mohr-Coulomb model, limiting states of stress are described by means of the friction angle phi, the cohesion c and the dilatancy angle psi. However, soil stiffness is described much more accurately by using three different input stiffnesses: the triaxial stiffness E50, the triaxial unloading stiffness Eur and the oedometer loading stiffness Eoed. In contrast to the Mohr-Coulomb model, the Hardening Soil model also accounts for stress-dependency of stiffness moduli. This means that all stiffnesses increase with pressure. Hence, all three input stiffnesses relate to a reference stress, usually taken as 100 kPa (1 Bar).
Besides the model parameters mentioned above, initial soil conditions, such as preconsolidation, play an essential role in most soil deformation problems. This can be taken into account in the initial stress generation.
The Hardening Soil model: Formulation and Verification
Triaxial test with Hardening Soil model
UDSM - Generalized Hardening Soil Model